molecules Review The Hedyotis diffusa Willd. (Rubiaceae): A Review on Phytochemistry, Pharmacology, Quality Control and Pharmacokinetics Rui Chen 1,2, Jingyu He 3, Xueli Tong 1,2, Lan Tang 1,2 and Menghua Liu 1,2,* 1 State Key Laboratory of Organ Failure Research, Guangdong Provincial Institute of Nephrology, Southern Medical University, Guangzhou 510515, Guangdong, China; [email protected] (R.C.); [email protected] (X.T.); [email protected] (L.T.) 2 Guangdong Provincial Key Laboratory of New Drug Screening, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou 510515, Guangdong, China 3 Bioengineering Research Centre, Guangzhou Institute of Advanced Technology, Chinese Academy of Sciences, Guangzhou 511458, Guangdong, China; [email protected] * Correspondence: [email protected]; Tel.: +86-20-6164-8597; Fax: +86-20-2291-2525 Academic Editor: Christopher W.K. Lam Received: 26 April 2016; Accepted: 24 May 2016; Published: 30 May 2016 Abstract: Hedyotis diffusa Willd (H. diffusa) is a well-known Chinese medicine with a variety of activities, especially its anti-cancer effect in the clinic. Up to now, 171 compounds have been reported from H. diffusa, including 32 iridoids, 26 flavonoids, 24 anthraquinones, 26 phenolics and their derivatives, 50 volatile oils and 13 miscellaneous compounds. In vitro and in vivo studies show these phytochemicals and plant extracts to exhibit a range of pharmacological activities of anti-cancer, antioxidant, anti-inflammatory, anti-fibroblast, immunomodulatory and neuroprotective effects. Although a series of methods have been established for the quality control of H. diffusa, a feasible and reliable approach is still needed in consideration of its botanical origin, collecting time and bioactive effects. Meanwhile, more pharmacokinetics researches are needed to illustrate the characteristics of H. diffusa in vivo. The present review aims to provide up-to-date and comprehensive information on the phytochemistry, pharmacology, quality control and pharmacokinetic characteristics of H. diffusa for its clinical use and further development. Keywords: H. diffusa; phytochemistry; pharmacology; quality control; pharmacokinetics 1. Introduction Hedyotis diffusa Willd (H. diffusa, Family Rubiaceae), known as Oldenlandia diffusa (Willd) Roxb, is a well-known Chinese medicine used for the treatment of inflammation-linked diseases, such as hepatitis, appendicitis and urethritis, for thousands of years in China [1]. In our previous studies, the water extract of H. diffusa has been proved to have an obvious protective effect in lipopolysaccharide-induced renal inflammation in mice. Recently, H. diffusa has gained increasing attention for its properties of anti-proliferative activity in cancer cells and anti-tumor activity in tumor-bearing animals [2–5]. It has been proved as the most commonly prescribed single Chinese herb used for colon cancer and breast cancer patients [6,7], according to the statistics from the National Health Insurance Research Database of Taiwan. H. diffusa is an annual herb, widely distributed in the orient and tropical Asia, such as China, Japan and Indonesia [1,8]. Generally, the plant grows in humid fields and ridges of farmlands, ascending to procumbent, to 50 cm tall; the stem is slightly flattened to terete, glabrescent to glabrous and the papilla was observed in the transverse section of the stem; the leaves are opposite, sessile or subsessile and blade drying membranous, linear, narrowly elliptic, 1–4 ˆ 0.1–0.4 cm; the flowers with pedicels are Molecules 2016, 21, 710; doi:10.3390/molecules21060710 www.mdpi.com/journal/molecules Molecules 2016, 21, 710 2 of 30 pairs in axillary racemes and the corolla is white [1,9]. Together with these phenotypic characteristics of H. diffusa, methods of thin-layer chromatography (TLC) [10], gas chromatography-mass spectrometer (GC-MS) [11], high performance liquid chromatography (HPLC) [9] and DNA sequencing [8,12] have been developed to differentiate H. diffusa from related species (e.g., Hedyotis corymbosa (L.) Lam) to give the right prescription for illnesses. Although there are numbers of published scientific literature on the chemical constituents, pharmacological activities and quantitative analysis of H. diffusa, a systematic and updated review is unavailable. Therefore, the aim of this review is to extensively summarize the phytochemistry, pharmacology, quality control and pharmacokinetic characteristics of H. diffusa, as well as being an evidence for clinical uses and further researches of this herb. 2. Phytochemistry With the advancement of analysis technologies like mass spectrometer (MS), liquid chromatograph–mass spectrometer (LC-MS), nuclear magnetic resonance–mass spectrometer (NMR-MS) etc., many studies on H. diffusa revealed numbers of important phytochemicals, including iridoids, triterpenes, flavonoids, anthraquinones, phenolic acids and their derivatives, sterols, alkaloids, volatile oils, polysaccharides, cyclotides, coumarins and alkaloids. The detailed information for these compounds is summarized in Table1. Table 1. Compounds of the H. diffusa. NO. Compound Name Molecular Formula Reference Iridoids 1 Asperuloside C18H22O11 [13,14] 2 Deacetyl asperuloside C16H20O10 [15] 3 Asperuloside acid C18H24O12 [16] 4 Deacetyl asperulosidic acid C16H22O11 [15] 5 Deacetyl asperulosidic acid methyl ester C17H24O11 [15,17] 6 Geniposidic acid C16H22O10 [18] 7 10-O-Acetyl geniposidic acid C18H24O11 [15] 8 10-Dehydro geniposide C17H22O10 [17] 9 10-Dehydro geniposidic acid C16H20O10 [19] 10 Diffusoside A C19H28O11 [20] 11 Diffusoside B C19H28O11 [20] 12 Lupenylacetate C32H52O2 [21] 13 Alpigenoside C18H28O12 [15] 14 Oldenlandoside III C34H44O20 [22] 15 5-O-Feruloyl scandoside methyl ester C27H32O14 [23] 16 Hehycoryside C C23H26O11 [22] 17 6-α-Hydro scandoside C16H22O11 [24] 18 6-β-Hydro scandoside C16H22O11 [24] 19 6-Dehydro scandoside C16H22O10 [19] 20 6-α-Hydro scandoside methyl ester C17H24O11 [24] 21 6-β-Hydro scandoside methyl ester C17H24O11 [24] 22 6-α-Hydro-10-acetyl asperuloside acid C18H24O12 [24] 23 6-β-Hydro-10-acetyl asperuloside acid C18H24O12 [24] 24 6-O-Methoxyl cinnamoyl scandoside C27H32O13 [23] 25 6-O-p-Hydro cinnamoyl scandoside C26H30O13 [23] (E)-6-O-p-Coumaroyl-10-O-formoxyl scandoside 26 C H O [14] methyl ester 27 32 13 27 (E)-6-O-p-Coumaroyl scandoside methyl ester C26H30O13 [14,15,25] 28 (Z)-6-O-p-Coumaroyl scandoside methyl ester C26H30O13 [18] 29 (E)-6-O-p-Methoxy cinnamoyl scandoside methyl ester C27H32O13 [15,25,26] 30 (Z)-6-O-p-Methoxy cinnamoyl scandoside methyl ester C27H32O13 [26] 31 (E)-6-O-Feruloyl scandoside methyl ester C27H32O14 [15,25,26] 32 (Z)-6-O-Feruloyl scandoside methyl ester C27H32O14 [27] Molecules 2016, 21, 710 3 of 30 Table 1. Cont. NO. Compound Name Molecular Formula Reference Triterpenes 33 Arborinone C30H48O[28] 34 Isoarborinol C30H50O[28] 35 Oleanolic acid C30H48O3 [19] 36 Ursolic acid C30H48O3 [19] Flavonoids 37 Amentoflavone C30H18O10 [26,29] 38 Chrysin-6-C-glucosyl-8-C-arabinosyl C26H28O13 [22] 39 Chrysin-6-C-arabinosyl-8-C-glucosyl C26H28O13 [22] 40 Oroxylin-A-O-glucuronic acid C22H20O11 [22] 41 Wogonin-O-glucuronic acid C22H20O11 [22] 42 5,7-Dihydroxy-3-methoxy flavonol C16H12O5 [13] 1 43 5,7,4 -Trihydroxy flavonol C15H10O6 [13] 1 1 44 5-Hydroxy-6,7,3 ,4 -tetramethoxy flavone C19H18O7 [21] 45 Quercetin C15H10O7 [17,19,30] 46 Rutin C27H30O16 [15,25,31] 47 Quercetin-3-O-β-D-glucopyranside C21H20O12 [25,32,33] 48 Quercetin-3-O-β-D-galactopyranoside C21H20O12 [32] 49 Quercetin-3-O-(2-O-glucopyranosyl)-β-D-glucopyranside C27H30O17 [15,25,32,33] 50 Quercetin-3-O-(2-O-glucopyranosyl)-β-D-galactopyranoside C27H30O17 [11,34] 51 Quercetin-3-O-sambubioside C26H28O16 [15,25] Quercetin-3-O-[2-O-(6-O-E-ferloyl)-β-D-glucopyranosyl]- 52 C37H38O20 [11,34] β-D-galactopyranoside Quercetin-3-O-[2-O-(6-O-E-feruloyl)-β-D-glucopyranosyl]- 53 C37H38O20 [11,15,25] β-D-glucopyanoside Quercetin-3-O-[2-O-(6-O-E-sinapoyl)-β-D-glucopyranosyl]- 54 C38H40O21 [15] β-D-glucopyanoside Quercetin-3-O-[2-O-(6-O-E-sinapoyl)-β-D-glucopyranosyl]- 55 C38H40O21 [25] β-D-galactopyranoside 56 Kaempferol C15H10O6 [17,35] 57 Kaempferol-3-O-β-D-glucopyranside C21H20O11 [32] 58 Kaempferol-3-O-β-D-galactopyranoside C21H20O11 [32] Kaempferol-3-O-(2-O-β-D-glucopyranosyl)- 59 C27H30O16 [11,25,34] β-D-galactopyranoside 60 Kaempferol-3-O-(6-O-α-L-rhamnosyl)-β-D-glucopyranside C27H30O16 [32] Kaempferol-3-O-[2-O-(E-6-O-feruloyl)-β-D-glucopyranosyl]- 61 C37H38O19 [11,25,33] β-D-glucopyranosyl Kaempferol-3-O-[2-O-(6-O-E-feruloyl)-β-D-glucopyranosyl]- 62 C37H38O19 [21,34] β-D-galactopyranoside Athraquinones 63 2-Methyl-3-methoxy anthraquinone C16H12O3 [19] 64 2-Hydroxy-1,3-dimethoxy anthraquinone C16H12O5 [29] 65 2-Hydroxy-3-methyl-1-methoxy anthraquinone C16H12O4 [36] 66 2-Hydroxy-3-methyl-4-methoxy anthraquinone C16H12O4 [37] 67 2-Hydroxy-7-methyl-3-methoxy anthraquinone C16H12O4 [36] 68 2-Hydroxy-1-methoxy-3-methyl anthraquinone C16H14O4 [31] 69 2-Hydroxy-3-methyl anthraquinone C15H10O3 [17,27] 70 2-Hydroxy-1-methoxy anthraquinone C15H10O4 [27,29] 71 2-Hydroxy-4-methoxy anthraquinone C15H10O4 [38] 72 2-Hydroxy-3-methoxy-7-methyl anthraquinone C16H12O4 [36] 73 2-Hydroxy-6-methyl anthraquinone C15H10O3 [18] 74 2-Hydroxy-3-methoxy-6-methyl anthraquinone C16H12O4 [18] 75 2,7-Dihydroxy-3-methyl anthraquinone C15H10O4 [39] 76 3-Hydroxy-2-methyl anthraquinone C15H10O3 [19] 77 3-Hydroxy-2-methyl-4-methoxy anthraquinone C16H12O4 [40] 78 2,3-Dimethoxy-6-methyl anthraquinone C17H14O4 [18] Molecules 2016, 21, 710 4 of 30 Table 1. Cont.